The present invention relates to draft tongues for towed implements and more specifically relates to draft tongues for towing a driven crop harvester from one side thereof so that the towing tractor follows a path which is offset to one side of the uncut crop and of a path followed by crop treating elements of the harvester.
It is a common practice when towing a crop harvester, such as a mower conditioner, for example, to connect a draft tongue to the left-hand side of the harvester frame. These tongues are usually straight, as viewed from above, and angle leftwardly and forwardly resulting in the driveline coupling the tractor PTO shaft to a gear box carried by the harvester making an angle of 15.degree.-25.degree. relative to the tractor centerline when the tractor is traveling straight ahead.
Two problems are presented by such structures. First, such harvesters must be able to turn sharply or tightly in order to mow all the crop in a corner. For example, the harvester should be capable of providing a 90.degree. turn while cutting without leaving uncut crop. In order to achieve this in a right-hand turn, the right-hand tire of the harvester must stop and pivot on a vertical axis at or near the left-hand tire. The turning radius of a tractor with a trailed implement is restricted by the rear tractor tire contacting the implement tongue. One way currently employed for allowing a tractor to undergo tight turns without interfering with the draft tongue is to provide a tractor drawbar extension which bolts to the drawbar. This moves the implement hitch pin further to the rear of the tractor rear axle and allows the tractor to turn tighter. However, the usage of such a drawbar extension has the disadvantage that the extension must be removed before hooking the tractor to other types of trailed implements.
Second, constantly operating the driveline at a substantial angle to the axis of the tractor PTO shaft when traveling straight ahead reduces the life of the driveline with the situation becoming worse when turning since the angle between the tractor PTO and the driveline increases in proportion to the degree of turn.